1. Field of the Invention
The present invention relates to an NOR type stack flash and over-erase verification and repair methods thereof.
2. Description of the Related Art
An NOR type stack flash requires an erase operation, to erase all storage cells to an identical value. However, some of the storage cells may be over-erased during the erase operation. The threshold voltage for the transistors (such as MOSs) of the over-erased storage cells is quite low, which results in current leakage.
To solve the current leakage problem, it is important to properly improve the over-erased storage cells.